Field of the Invention
This invention relates to a high compression strength honeycomb core and a method of making the core from a paper comprising p-aramid fiber and fibrids.
Description of Related Art
Core structures for sandwich panels from p-aramid fiber papers or wet-laid nonwovens, mostly in the form of honeycomb, are used in different applications but primarily in the aerospace industry where strength to weight or stiffness to weight ratios have very high values. Traditionally, such core structures have been optimized for maximum shear modulus (stiffness) of the core. For example, U.S. Pat. No. 5,137,768 to Lin describes a honeycomb core made from high-density paper comprising 50 weight percent or more of p-aramid fiber in the form of floc (cut fiber) with the rest of the composition being a binder and other additives.
In many cases, improved core shear properties have been achieved, without noticeable improvement in core compressive strength. In some instances, reduction in honeycomb core weight, while keeping the same or better shear properties, has led to some sacrifice in core compression strength. There is therefore an ongoing need for improved compression strength of honeycomb core based on p-aramid fiber paper.